The objective of this proposal is to determine whether dietary protein manipulation can be beneficial in preserving renal function following kidney irradiation. The specific aim is to examine, using a rat model, the interaction between radiation and diet by varying the level, quality and time course of lwo protein diets and also by varying the level and Let of radiation exposure. We will use immature uninephrectomized rats as our model, since such a system provides maximum stress on the remaining kidney and also is a good approximation of the clinical situation for patients with Wilms tumor. Several end points will be evaluated as measures of kidney function, including golmerular filtration rate (GFR), effective renal plasma flow (ERPF), urine specific gravity, urine production, and renal histology. GFR as determined by creatinine clearance will be calculated from measurements of serum creatinine levels and creatinine excretion in 24 hour urine samples. ERPF will be calculated from the plasma disappearance curve of iodinated ortho hippuran (IOH). Urine specific gravity will be measured on 24 hour urine samples and on urine collected after overnight water deprivation. Initial experiments will deal with the effects on renal function of 1) a low protein diet (LPD) 2) the LPD supplemented with essential amino acids (EEA) and 3) the LPD supplemented with amino acid analogs. Subsequent experiments will examine the consequences of several feeding time schedules, radiation fractionation and radiation quality. If the promise seen in our prior experiments continues to be born out in the work of this proposal, dietary protein modification may well prove to be a simple, safe, physiological method of reducing renal damage by radiation.